(1) Field of the invention
This invention relates generally to “on-site,” service, support, or recreational, “travel” trailers. More specifically to trailers that “drop-down” for more convenient access to the floor surface level, “expand laterally,” for a wider more spacious “feel” (while doubling the usable floor space area), and offer a high level of protection and structural strength by way of a well stressed coherent structure.
(2) Description of the Prior Art
Previous expansible trailers and trailers in general have their undercarriage (chassis), and “active,” (stressed) load carrying structures under the floor and “non active,” (static, compressive) “load” structures, above the floor. This conventional design utilizes inefficiently the volume of space (envelope) and the weight of construction materials consumed. Most of the trailer weight and stresses are carried by under floor framework, (frame-rails) that rest above springs, axles, wheels, etc. which consume space while raising floor level. Above floor structures are mostly compressive “load” in nature and add little to strength or sharing of stresses overall. Attempts to lower floor heights lead engineers to use inefficient multiple tandem axles with small diameter wheels and narrow cross section frame-rails (which allows bowing of said rails) yet still result in lost usable space (volume), high floor levels, and limited ceiling heights. This design “culture” also limits floor access to wheel chairs, loading, and general use (convenience). Previous expansible trailers also use internal walls and load bearing structures, which interfere with free and open spans. Another practice, accordion like floors and roofs, are bulky, clumsy, and require complex sealing and fastening means. Previous expansible trailers are leak prone, more likely to be blown over by wind due to height, awkward in appearance, and cannot lower the floor surface to a readily accessible one hundred twenty millimeters above the road surface when parked.